04. Split by Word Casing

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _04.Split_by_Word_Casing
{
    class SplitByWordCasing
    {
        static void Main(string[] args)
        {
            char[] separators = new char[] { ',', ';', ':', '.', '!', '(', ')', '\'', '\'', '\\', '/', '[', ']', ' ' };
            List<string> words = Console.ReadLine()
                .Split(separators, StringSplitOptions.RemoveEmptyEntries)
                .ToList();

            List<string> lowerCase = new List<string>();
            List<string> upperCase = new List<string>();
            List<string> mixedCase = new List<string>();

            foreach (var word in words)
            {
                if (isLower(word))
                {
                    lowerCase.Add(word);
                }
                else if (isUpper(word))
                {
                    upperCase.Add(word);
                }
                else
                {
                    mixedCase.Add(word);
                }
            }

            Console.WriteLine("Lower-case: " + string.Join(", ", lowerCase));
            Console.WriteLine("Mixed-case: " + string.Join(", ", mixedCase));
            Console.WriteLine("Upper-case: " + string.Join(", ", upperCase));
        }

        public static bool isLower(string word)
        {
            foreach (var letter in word)
            {
                if (!Char.IsLower(letter))
                {
                    return false;
                }
            }
            return true;
        }

        public static bool isUpper(string word)
        {
            foreach (var letter in word)
            {
                if (!Char.IsUpper(letter))
                {
                    return false;
                }
            }
            return true;
        }
    }
}